Method and apparatus for intra block copy in intra-inter blending mode and triangle prediction unit mode

ABSTRACT

A method of video decoding includes creating a candidate list for a current block in a current picture included in a coded video bitstream. The method further includes determining a coding mode for a candidate block associated with the current block. The method further includes determining whether to add, to the candidate list, a vector associated the candidate block based on the determined coding mode. The method further includes reconstructing the current block using at least one candidate from the candidate list.

INCORPORATION BY REFERENCE

This present disclosure claims the benefit of priority to U.S.Provisional Application No. 62/743,967, “INTRA BLOCK COPY IN INTRA-INTERBLENDING MODE” filed on Oct. 10, 2018, and U.S. Provisional ApplicationNo. 62/743,933, “INTRA BLOCK COPY IN TRIANGLE PREDICTION UNIT MODE”filed on Oct. 10, 2018, which is incorporated by reference herein in itsentirety.

TECHNICAL FIELD

The present disclosure describes embodiments generally related to videocoding.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent the work is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

Video coding and decoding can be performed using inter-pictureprediction with motion compensation. Uncompressed digital video caninclude a series of pictures, each picture having a spatial dimensionof, for example, 1920×1080 luminance samples and associated chrominancesamples. The series of pictures can have a fixed or variable picturerate (informally also known as frame rate), of, for example 60 picturesper second or 60 Hz. Uncompressed video has significant bitraterequirements. For example, 1080p60 4:2:0 video at 8 bit per sample(1920×1080 luminance sample resolution at 60 Hz frame rate) requiresclose to 1.5 Gbit/s bandwidth. An hour of such video requires more than600 GBytes of storage space.

One purpose of video coding and decoding can be the reduction ofredundancy in the input video signal, through compression. Compressioncan help reduce the aforementioned bandwidth or storage spacerequirements, in some cases by two orders of magnitude or more. Bothlossless and lossy compression, as well as a combination thereof can beemployed. Lossless compression refers to techniques where an exact copyof the original signal can be reconstructed from the compressed originalsignal. When using lossy compression, the reconstructed signal may notbe identical to the original signal, but the distortion between originaland reconstructed signals is small enough to make the reconstructedsignal useful for the intended application. In the case of video, lossycompression is widely employed. The amount of distortion tolerateddepends on the application; for example, users of certain consumerstreaming applications may tolerate higher distortion than users oftelevision distribution applications. The compression ratio achievablecan reflect that: higher allowable/tolerable distortion can yield highercompression ratios.

Motion compensation can be a lossy compression technique and can relateto techniques where a block of sample data from a previouslyreconstructed picture or part thereof (reference picture), after beingspatially shifted in a direction indicated by a motion vector (MVhenceforth), is used for the prediction of a newly reconstructed pictureor picture part. In some cases, the reference picture can be the same asthe picture currently under reconstruction. MVs can have two dimensionsX and Y, or three dimensions, the third being an indication of thereference picture in use (the latter, indirectly, can be a timedimension).

In some video compression techniques, an MV applicable to a certain areaof sample data can be predicted from other MVs, for example from thoserelated to another area of sample data spatially adjacent to the areaunder reconstruction, and preceding that MV in decoding order. Doing socan substantially reduce the amount of data required for coding the MV,thereby removing redundancy and increasing compression. MV predictioncan work effectively, for example, because when coding an input videosignal derived from a camera (known as natural video) there is astatistical likelihood that areas larger than the area to which a singleMV is applicable move in a similar direction and, therefore, can in somecases be predicted using a similar motion vector derived from MVs ofneighboring area. That results in the MV found for a given area to besimilar or the same as the MV predicted from the surrounding MVs, andthat in turn can be represented, after entropy coding, in a smallernumber of bits than what would be used if coding the MV directly. Insome cases, MV prediction can be an example of lossless compression of asignal (namely: the MVs) derived from the original signal (namely: thesample stream). In other cases, MV prediction itself can be lossy, forexample because of rounding errors when calculating a predictor fromseveral surrounding MVs.

Various MV prediction mechanisms are described in H.265/HEVC (ITU-T Rec.H.265, “High Efficiency Video Coding”, December 2016). Out of the manyMV prediction mechanisms that H.265 offers, described here is atechnique henceforth referred to as “spatial merge”.

Referring to FIG. 1, a current block (101) comprises samples that havebeen found by the encoder during the motion search process to bepredictable from a previous block of the same size that has beenspatially shifted. Instead of coding that MV directly, the MV can bederived from metadata associated with one or more reference pictures,for example from the most recent (in decoding order) reference picture,using the MV associated with either one of five surrounding samples,denoted A0, A1, and B0, B1, B2 (102 through 106, respectively). InH.265, the MV prediction can use predictors from the same referencepicture that the neighboring block is using.

SUMMARY

According to an exemplary embodiment, a method of video decodingincludes creating a candidate list for a current block in a currentpicture included in a coded video bitstream. The method further includesdetermining a coding mode for a candidate block associated with thecurrent block. The method further includes determining whether to add,to the candidate list, a vector associated the candidate block based onthe determined coding mode. The method further includes reconstructingthe current block using at least one candidate from the candidate list.

According to an exemplary embodiment, a video decoder for video decodingincludes processing circuitry configured to create a candidate list fora current block in a current picture included in a coded videobitstream. The processing circuitry is further configured to determine acoding mode for a candidate block associated with the current block. Theprocessing circuitry is further configured to determine whether to add,to the candidate list, a vector associated the candidate block based onthe determined coding mode. The processing circuitry is furtherconfigured to reconstruct the current block using at least one candidatefrom the candidate list.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, the nature, and various advantages of the disclosedsubject matter will be more apparent from the following detaileddescription and the accompanying drawings in which:

FIG. 1 is a schematic illustration of a current block and itssurrounding spatial merge candidates in one example.

FIG. 2 is a schematic illustration of a simplified block diagram of acommunication system (200) in accordance with an embodiment.

FIG. 3 is a schematic illustration of a simplified block diagram of acommunication system (300) in accordance with an embodiment.

FIG. 4 is a schematic illustration of a simplified block diagram of adecoder in accordance with an embodiment.

FIG. 5 is a schematic illustration of a simplified block diagram of anencoder in accordance with an embodiment.

FIG. 6 shows a block diagram of an encoder in accordance with anotherembodiment.

FIG. 7 shows a block diagram of a decoder in accordance with anotherembodiment.

FIG. 8 is a schematic illustration of intra picture block compensationin accordance with an embodiment.

FIG. 9 is a schematic illustration of intra-inter blending mode inaccordance with an embodiment of the present disclosure.

FIG. 10 is a schematic illustration of two splitting examples for acurrent block according to a triangle prediction unit mode in accordancewith an embodiment of the present disclosure.

FIG. 11 is a schematic illustration of a block with spatial and temporalneighbors in accordance with an embodiment of the present disclosure.

FIG. 12 is a schematic illustration of blocks with applied weightingfactors in accordance with embodiments of the present disclosure.

FIG. 13 is a schematic illustration of motion vector storage inaccordance with embodiments of the present disclosure.

FIG. 14 shows a flow chart of a decoding process in accordance with anembodiment of the present disclosure.

FIG. 15 is a schematic illustration of a computer system in accordancewith an embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 2 illustrates a simplified block diagram of a communication system(200) according to an embodiment of the present disclosure. Thecommunication system (200) includes a plurality of terminal devices thatcan communicate with each other, via, for example, a network (250). Forexample, the communication system (200) includes a first pair ofterminal devices (210) and (220) interconnected via the network (250).In the FIG. 2 example, the first pair of terminal devices (210) and(220) performs unidirectional transmission of data. For example, theterminal device (210) may code video data (e.g., a stream of videopictures that are captured by the terminal device (210)) fortransmission to the other terminal device (220) via the network (250).The encoded video data can be transmitted in the form of one or morecoded video bitstreams. The terminal device (220) may receive the codedvideo data from the network (250), decode the coded video data torecover the video pictures and display video pictures according to therecovered video data. Unidirectional data transmission may be common inmedia serving applications and the like.

In another example, the communication system (200) includes a secondpair of terminal devices (230) and (240) that performs bidirectionaltransmission of coded video data that may occur, for example, duringvideoconferencing. For bidirectional transmission of data, in anexample, each terminal device of the terminal devices (230) and (240)may code video data (e.g., a stream of video pictures that are capturedby the terminal device) for transmission to the other terminal device ofthe terminal devices (230) and (240) via the network (250). Eachterminal device of the terminal devices (230) and (240) also may receivethe coded video data transmitted by the other terminal device of theterminal devices (230) and (240), and may decode the coded video data torecover the video pictures and may display video pictures at anaccessible display device according to the recovered video data.

In the FIG. 2 example, the terminal devices (210), (220), (230) and(240) may be illustrated as servers, personal computers and smart phonesbut the principles of the present disclosure may be not so limited.Embodiments of the present disclosure find application with laptopcomputers, tablet computers, media players and/or dedicated videoconferencing equipment. The network (250) represents any number ofnetworks that convey coded video data among the terminal devices (210),(220), (230) and (240), including for example wireline (wired) and/orwireless communication networks. The communication network (250) mayexchange data in circuit-switched and/or packet-switched channels.Representative networks include telecommunications networks, local areanetworks, wide area networks and/or the Internet. For the purposes ofthe present discussion, the architecture and topology of the network(250) may be immaterial to the operation of the present disclosureunless explained herein below.

FIG. 3 illustrates, as an example for an application for the disclosedsubject matter, the placement of a video encoder and a video decoder ina streaming environment. The disclosed subject matter can be equallyapplicable to other video enabled applications, including, for example,video conferencing, digital TV, storing of compressed video on digitalmedia including CD, DVD, memory stick and the like, and so on.

A streaming system may include a capture subsystem (313), that caninclude a video source (301), for example a digital camera, creating forexample a stream of video pictures (302) that are uncompressed. In anexample, the stream of video pictures (302) includes samples that aretaken by the digital camera. The stream of video pictures (302),depicted as a bold line to emphasize a high data volume when compared toencoded video data (304) (or coded video bitstreams), can be processedby an electronic device (320) that includes a video encoder (303)coupled to the video source (301). The video encoder (303) can includehardware, software, or a combination thereof to enable or implementaspects of the disclosed subject matter as described in more detailbelow. The encoded video data (304) (or encoded video bitstream (304)),depicted as a thin line to emphasize the lower data volume when comparedto the stream of video pictures (302), can be stored on a streamingserver (305) for future use. One or more streaming client subsystems,such as client subsystems (306) and (308) in FIG. 3 can access thestreaming server (305) to retrieve copies (307) and (309) of the encodedvideo data (304). A client subsystem (306) can include a video decoder(310), for example, in an electronic device (330). The video decoder(310) decodes the incoming copy (307) of the encoded video data andcreates an outgoing stream of video pictures (311) that can be renderedon a display (312) (e.g., display screen) or other rendering device (notdepicted). In some streaming systems, the encoded video data (304),(307), and (309) (e.g., video bitstreams) can be encoded according tocertain video coding/compression standards. Examples of those standardsinclude ITU-T Recommendation H.265. In an example, a video codingstandard under development is informally known as Versatile Video Coding(VVC). The disclosed subject matter may be used in the context of VVC.

It is noted that the electronic devices (320) and (330) can includeother components (not shown). For example, the electronic device (320)can include a video decoder (not shown) and the electronic device (330)can include a video encoder (not shown) as well.

FIG. 4 shows a block diagram of a video decoder (410) according to anembodiment of the present disclosure. The video decoder (410) can beincluded in an electronic device (430). The electronic device (430) caninclude a receiver (431) (e.g., receiving circuitry). The video decoder(410) can be used in the place of the video decoder (310) in the FIG. 3example.

The receiver (431) may receive one or more coded video sequences to bedecoded by the video decoder (410); in the same or another embodiment,one coded video sequence at a time, where the decoding of each codedvideo sequence is independent from other coded video sequences. Thecoded video sequence may be received from a channel (401), which may bea hardware/software link to a storage device which stores the encodedvideo data. The receiver (431) may receive the encoded video data withother data, for example, coded audio data and/or ancillary data streams,that may be forwarded to their respective using entities (not depicted).The receiver (431) may separate the coded video sequence from the otherdata. To combat network jitter, a buffer memory (415) may be coupled inbetween the receiver (431) and an entropy decoder/parser (420) (“parser(420)” henceforth). In certain applications, the buffer memory (415) ispart of the video decoder (410). In others, it can be outside of thevideo decoder (410) (not depicted). In still others, there can be abuffer memory (not depicted) outside of the video decoder (410), forexample to combat network jitter, and in addition another buffer memory(415) inside the video decoder (410), for example to handle playouttiming. When the receiver (431) is receiving data from a store/forwarddevice of sufficient bandwidth and controllability, or from anisosynchronous network, the buffer memory (415) may not be needed, orcan be small. For use on best effort packet networks such as theInternet, the buffer memory (415) may be required, can be comparativelylarge and can be advantageously of adaptive size, and may at leastpartially be implemented in an operating system or similar elements (notdepicted) outside of the video decoder (410).

The video decoder (410) may include the parser (420) to reconstructsymbols (421) from the coded video sequence. Categories of those symbolsinclude information used to manage operation of the video decoder (410),and potentially information to control a rendering device such as arender device (412) (e.g., a display screen) that is not an integralpart of the electronic device (430) but can be coupled to the electronicdevice (430), as was shown in FIG. 4. The control information for therendering device(s) may be in the form of Supplemental EnhancementInformation (SEI messages) or Video Usability Information (VUI)parameter set fragments (not depicted). The parser (420) mayparse/entropy-decode the coded video sequence that is received. Thecoding of the coded video sequence can be in accordance with a videocoding technology or standard, and can follow various principles,including variable length coding, Huffman coding, arithmetic coding withor without context sensitivity, and so forth. The parser (420) mayextract from the coded video sequence, a set of subgroup parameters forat least one of the subgroups of pixels in the video decoder, based uponat least one parameter corresponding to the group. Subgroups can includeGroups of Pictures (GOPs), pictures, tiles, slices, macroblocks, CodingUnits (CUs), blocks, Transform Units (TUs), Prediction Units (PUs) andso forth. The parser (420) may also extract from the coded videosequence information such as transform coefficients, quantizer parametervalues, motion vectors, and so forth.

The parser (420) may perform an entropy decoding/parsing operation onthe video sequence received from the buffer memory (415), so as tocreate symbols (421).

Reconstruction of the symbols (421) can involve multiple different unitsdepending on the type of the coded video picture or parts thereof (suchas: inter and intra picture, inter and intra block), and other factors.Which units are involved, and how, can be controlled by the subgroupcontrol information that was parsed from the coded video sequence by theparser (420). The flow of such subgroup control information between theparser (420) and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, the video decoder (410)can be conceptually subdivided into a number of functional units asdescribed below. In a practical implementation operating undercommercial constraints, many of these units interact closely with eachother and can, at least partly, be integrated into each other. However,for the purpose of describing the disclosed subject matter, theconceptual subdivision into the functional units below is appropriate.

A first unit is the scaler/inverse transform unit (451). Thescaler/inverse transform unit (451) receives a quantized transformcoefficient as well as control information, including which transform touse, block size, quantization factor, quantization scaling matrices,etc. as symbol(s) (421) from the parser (420). The scaler/inversetransform unit (451) can output blocks comprising sample values, thatcan be input into aggregator (455).

In some cases, the output samples of the scaler/inverse transform (451)can pertain to an intra coded block; that is: a block that is not usingpredictive information from previously reconstructed pictures, but canuse predictive information from previously reconstructed parts of thecurrent picture. Such predictive information can be provided by an intrapicture prediction unit (452). In some cases, the intra pictureprediction unit (452) generates a block of the same size and shape ofthe block under reconstruction, using surrounding already reconstructedinformation fetched from the current picture buffer (458). The currentpicture buffer (458) buffers, for example, partly reconstructed currentpicture and/or fully reconstructed current picture. The aggregator(455), in some cases, adds, on a per sample basis, the predictioninformation the intra prediction unit (452) has generated to the outputsample information as provided by the scaler/inverse transform unit(451).

In other cases, the output samples of the scaler/inverse transform unit(451) can pertain to an inter coded, and potentially motion compensatedblock. In such a case, a motion compensation prediction unit (453) canaccess reference picture memory (457) to fetch samples used forprediction. After motion compensating the fetched samples in accordancewith the symbols (421) pertaining to the block, these samples can beadded by the aggregator (455) to the output of the scaler/inversetransform unit (451) (in this case called the residual samples orresidual signal) so as to generate output sample information. Theaddresses within the reference picture memory (457) from where themotion compensation prediction unit (453) fetches prediction samples canbe controlled by motion vectors, available to the motion compensationprediction unit (453) in the form of symbols (421) that can have, forexample X, Y, and reference picture components. Motion compensation alsocan include interpolation of sample values as fetched from the referencepicture memory (457) when sub-sample exact motion vectors are in use,motion vector prediction mechanisms, and so forth.

The output samples of the aggregator (455) can be subject to variousloop filtering techniques in the loop filter unit (456). Videocompression technologies can include in-loop filter technologies thatare controlled by parameters included in the coded video sequence (alsoreferred to as coded video bitstream) and made available to the loopfilter unit (456) as symbols (421) from the parser (420), but can alsobe responsive to meta-information obtained during the decoding ofprevious (in decoding order) parts of the coded picture or coded videosequence, as well as responsive to previously reconstructed andloop-filtered sample values.

The output of the loop filter unit (456) can be a sample stream that canbe output to the render device (412) as well as stored in the referencepicture memory (457) for use in future inter-picture prediction.

Certain coded pictures, once fully reconstructed, can be used asreference pictures for future prediction. For example, once a codedpicture corresponding to a current picture is fully reconstructed andthe coded picture has been identified as a reference picture (by, forexample, the parser (420)), the current picture buffer (458) can becomea part of the reference picture memory (457), and a fresh currentpicture buffer can be reallocated before commencing the reconstructionof the following coded picture.

The video decoder (410) may perform decoding operations according to apredetermined video compression technology in a standard, such as ITU-TRec. H.265. The coded video sequence may conform to a syntax specifiedby the video compression technology or standard being used, in the sensethat the coded video sequence adheres to both the syntax of the videocompression technology or standard and the profiles as documented in thevideo compression technology or standard. Specifically, a profile canselect certain tools as the only tools available for use under thatprofile from all the tools available in the video compression technologyor standard. Also necessary for compliance can be that the complexity ofthe coded video sequence is within bounds as defined by the level of thevideo compression technology or standard. In some cases, levels restrictthe maximum picture size, maximum frame rate, maximum reconstructionsample rate (measured in, for example megasamples per second), maximumreference picture size, and so on. Limits set by levels can, in somecases, be further restricted through Hypothetical Reference Decoder(HRD) specifications and metadata for HRD buffer management signaled inthe coded video sequence.

In an embodiment, the receiver (431) may receive additional (redundant)data with the encoded video. The additional data may be included as partof the coded video sequence(s). The additional data may be used by thevideo decoder (410) to properly decode the data and/or to moreaccurately reconstruct the original video data. Additional data can bein the form of, for example, temporal, spatial, or signal noise ratio(SNR) enhancement layers, redundant slices, redundant pictures, forwarderror correction codes, and so on.

FIG. 5 shows a block diagram of a video encoder (503) according to anembodiment of the present disclosure. The video encoder (503) isincluded in an electronic device (520). The electronic device (520)includes a transmitter (540) (e.g., transmitting circuitry). The videoencoder (503) can be used in the place of the video encoder (303) in theFIG. 3 example.

The video encoder (503) may receive video samples from a video source(501) (that is not part of the electronic device (520) in the FIG. 5example) that may capture video image(s) to be coded by the videoencoder (503). In another example, the video source (501) is a part ofthe electronic device (520).

The video source (501) may provide the source video sequence to be codedby the video encoder (503) in the form of a digital video sample streamthat can be of any suitable bit depth (for example: 8 bit, 10 bit, 12bit, . . . ), any colorspace (for example, BT.601 Y CrCB, RGB, . . . ),and any suitable sampling structure (for example Y CrCb 4:2:0, Y CrCb4:4:4). In a media serving system, the video source (501) may be astorage device storing previously prepared video. In a videoconferencingsystem, the video source (501) may be a camera that captures local imageinformation as a video sequence. Video data may be provided as aplurality of individual pictures that impart motion when viewed insequence. The pictures themselves may be organized as a spatial array ofpixels, wherein each pixel can comprise one or more samples depending onthe sampling structure, color space, etc. in use. A person skilled inthe art can readily understand the relationship between pixels andsamples. The description below focuses on samples.

According to an embodiment, the video encoder (503) may code andcompress the pictures of the source video sequence into a coded videosequence (543) in real time or under any other time constraints asrequired by the application. Enforcing appropriate coding speed is onefunction of a controller (550). In some embodiments, the controller(550) controls other functional units as described below and isfunctionally coupled to the other functional units. The coupling is notdepicted for clarity. Parameters set by the controller (550) can includerate control related parameters (picture skip, quantizer, lambda valueof rate-distortion optimization techniques, . . . ), picture size, groupof pictures (GOP) layout, maximum motion vector search range, and soforth. The controller (550) can be configured to have other suitablefunctions that pertain to the video encoder (503) optimized for acertain system design.

In some embodiments, the video encoder (503) is configured to operate ina coding loop. As an oversimplified description, in an example, thecoding loop can include a source coder (530) (e.g., responsible forcreating symbols, such as a symbol stream, based on an input picture tobe coded, and a reference picture(s)), and a (local) decoder (533)embedded in the video encoder (503). The decoder (533) reconstructs thesymbols to create the sample data in a similar manner as a (remote)decoder also would create (as any compression between symbols and codedvideo bitstream is lossless in the video compression technologiesconsidered in the disclosed subject matter). The reconstructed samplestream (sample data) is input to the reference picture memory (534). Asthe decoding of a symbol stream leads to bit-exact results independentof decoder location (local or remote), the content in the referencepicture memory (534) is also bit exact between the local encoder andremote encoder. In other words, the prediction part of an encoder “sees”as reference picture samples exactly the same sample values as a decoderwould “see” when using prediction during decoding. This fundamentalprinciple of reference picture synchronicity (and resulting drift, ifsynchronicity cannot be maintained, for example because of channelerrors) is used in some related arts as well.

The operation of the “local” decoder (533) can be the same as of a“remote” decoder, such as the video decoder (410), which has alreadybeen described in detail above in conjunction with FIG. 4. Brieflyreferring also to FIG. 4, however, as symbols are available andencoding/decoding of symbols to a coded video sequence by an entropycoder (545) and the parser (420) can be lossless, the entropy decodingparts of the video decoder (410), including the buffer memory (415), andparser (420) may not be fully implemented in the local decoder (533).

An observation that can be made at this point is that any decodertechnology except the parsing/entropy decoding that is present in adecoder also necessarily needs to be present, in substantially identicalfunctional form, in a corresponding encoder. For this reason, thedisclosed subject matter focuses on decoder operation. The descriptionof encoder technologies can be abbreviated as they are the inverse ofthe comprehensively described decoder technologies. Only in certainareas a more detail description is required and provided below.

During operation, in some examples, the source coder (530) may performmotion compensated predictive coding, which codes an input picturepredictively with reference to one or more previously-coded picture fromthe video sequence that were designated as “reference pictures”. In thismanner, the coding engine (532) codes differences between pixel blocksof an input picture and pixel blocks of reference picture(s) that may beselected as prediction reference(s) to the input picture.

The local video decoder (533) may decode coded video data of picturesthat may be designated as reference pictures, based on symbols createdby the source coder (530). Operations of the coding engine (532) mayadvantageously be lossy processes. When the coded video data may bedecoded at a video decoder (not shown in FIG. 5), the reconstructedvideo sequence typically may be a replica of the source video sequencewith some errors. The local video decoder (533) replicates decodingprocesses that may be performed by the video decoder on referencepictures and may cause reconstructed reference pictures to be stored inthe reference picture cache (534). In this manner, the video encoder(503) may store copies of reconstructed reference pictures locally thathave common content as the reconstructed reference pictures that will beobtained by a far-end video decoder (absent transmission errors).

The predictor (535) may perform prediction searches for the codingengine (532). That is, for a new picture to be coded, the predictor(535) may search the reference picture memory (534) for sample data (ascandidate reference pixel blocks) or certain metadata such as referencepicture motion vectors, block shapes, and so on, that may serve as anappropriate prediction reference for the new pictures. The predictor(535) may operate on a sample block-by-pixel block basis to findappropriate prediction references. In some cases, as determined bysearch results obtained by the predictor (535), an input picture mayhave prediction references drawn from multiple reference pictures storedin the reference picture memory (534).

The controller (550) may manage coding operations of the source coder(530), including, for example, setting of parameters and subgroupparameters used for encoding the video data.

Output of all aforementioned functional units may be subjected toentropy coding in the entropy coder (545). The entropy coder (545)translates the symbols as generated by the various functional units intoa coded video sequence, by lossless compressing the symbols according totechnologies such as Huffman coding, variable length coding, arithmeticcoding, and so forth.

The transmitter (540) may buffer the coded video sequence(s) as createdby the entropy coder (545) to prepare for transmission via acommunication channel (560), which may be a hardware/software link to astorage device which would store the encoded video data. The transmitter(540) may merge coded video data from the video coder (503) with otherdata to be transmitted, for example, coded audio data and/or ancillarydata streams (sources not shown).

The controller (550) may manage operation of the video encoder (503).During coding, the controller (550) may assign to each coded picture acertain coded picture type, which may affect the coding techniques thatmay be applied to the respective picture. For example, pictures oftenmay be assigned as one of the following picture types:

An Intra Picture (I picture) may be one that may be coded and decodedwithout using any other picture in the sequence as a source ofprediction. Some video codecs allow for different types of intrapictures, including, for example Independent Decoder Refresh (“IDR”)Pictures. A person skilled in the art is aware of those variants of Ipictures and their respective applications and features.

A predictive picture (P picture) may be one that may be coded anddecoded using intra prediction or inter prediction using at most onemotion vector and reference index to predict the sample values of eachblock.

A bi-directionally predictive picture (B Picture) may be one that may becoded and decoded using intra prediction or inter prediction using atmost two motion vectors and reference indices to predict the samplevalues of each block. Similarly, multiple-predictive pictures can usemore than two reference pictures and associated metadata for thereconstruction of a single block.

Source pictures commonly may be subdivided spatially into a plurality ofsample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 sampleseach) and coded on a block-by-block basis. Blocks may be codedpredictively with reference to other (already coded) blocks asdetermined by the coding assignment applied to the blocks' respectivepictures. For example, blocks of I pictures may be codednon-predictively or they may be coded predictively with reference toalready coded blocks of the same picture (spatial prediction or intraprediction). Pixel blocks of P pictures may be coded predictively, viaspatial prediction or via temporal prediction with reference to onepreviously coded reference picture. Blocks of B pictures may be codedpredictively, via spatial prediction or via temporal prediction withreference to one or two previously coded reference pictures.

The video encoder (503) may perform coding operations according to apredetermined video coding technology or standard, such as ITU-T Rec.H.265. In its operation, the video encoder (503) may perform variouscompression operations, including predictive coding operations thatexploit temporal and spatial redundancies in the input video sequence.The coded video data, therefore, may conform to a syntax specified bythe video coding technology or standard being used.

In an embodiment, the transmitter (540) may transmit additional datawith the encoded video. The source coder (530) may include such data aspart of the coded video sequence. Additional data may comprisetemporal/spatial/SNR enhancement layers, other forms of redundant datasuch as redundant pictures and slices, SEI messages, VUI parameter setfragments, and so on.

A video may be captured as a plurality of source pictures (videopictures) in a temporal sequence. Intra-picture prediction (oftenabbreviated to intra prediction) makes use of spatial correlation in agiven picture, and inter-picture prediction makes uses of the (temporalor other) correlation between the pictures. In an example, a specificpicture under encoding/decoding, which is referred to as a currentpicture, is partitioned into blocks. When a block in the current pictureis similar to a reference block in a previously coded and still bufferedreference picture in the video, the block in the current picture can becoded by a vector that is referred to as a motion vector. The motionvector points to the reference block in the reference picture, and canhave a third dimension identifying the reference picture, in casemultiple reference pictures are in use.

In some embodiments, a bi-prediction technique can be used in theinter-picture prediction. According to the bi-prediction technique, tworeference pictures, such as a first reference picture and a secondreference picture that are both prior in decoding order to the currentpicture in the video (but may be in the past and future, respectively,in display order) are used. A block in the current picture can be codedby a first motion vector that points to a first reference block in thefirst reference picture, and a second motion vector that points to asecond reference block in the second reference picture. The block can bepredicted by a combination of the first reference block and the secondreference block.

Further, a merge mode technique can be used in the inter-pictureprediction to improve coding efficiency.

According to some embodiments of the disclosure, predictions, such asinter-picture predictions and intra-picture predictions are performed inthe unit of blocks. For example, according to the HEVC standard, apicture in a sequence of video pictures is partitioned into coding treeunits (CTU) for compression, the CTUs in a picture have the same size,such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. In general, a CTUincludes three coding tree blocks (CTBs), which are one luma CTB and twochroma CTBs. Each CTU can be recursively quadtree split into one ormultiple coding units (CUs). For example, a CTU of 64×64 pixels can besplit into one CU of 64×64 pixels, or 4 CUs of 32×32 pixels, or 16 CUsof 16×16 pixels. In an example, each CU is analyzed to determine aprediction type for the CU, such as an inter prediction type or an intraprediction type. The CU is split into one or more prediction units (PUs)depending on the temporal and/or spatial predictability. Generally, eachPU includes a luma prediction block (PB), and two chroma PBs. In anembodiment, a prediction operation in coding (encoding/decoding) isperformed in the unit of a prediction block. Using a luma predictionblock as an example of a prediction block, the prediction block includesa matrix of values (e.g., luma values) for pixels, such as 8×8 pixels,16×16 pixels, 8×16 pixels, 16×8 pixels, and the like.

FIG. 6 shows a diagram of a video encoder (603) according to anotherembodiment of the disclosure. The video encoder (603) is configured toreceive a processing block (e.g., a prediction block) of sample valueswithin a current video picture in a sequence of video pictures, andencode the processing block into a coded picture that is part of a codedvideo sequence. In an example, the video encoder (603) is used in theplace of the video encoder (303) in the FIG. 3 example.

In an HEVC example, the video encoder (603) receives a matrix of samplevalues for a processing block, such as a prediction block of 8×8samples, and the like. The video encoder (603) determines whether theprocessing block is best coded using intra mode, inter mode, orbi-prediction mode using, for example, rate-distortion optimization.When the processing block is to be coded in intra mode, the videoencoder (603) may use an intra prediction technique to encode theprocessing block into the coded picture; and when the processing blockis to be coded in inter mode or bi-prediction mode, the video encoder(603) may use an inter prediction or bi-prediction technique,respectively, to encode the processing block into the coded picture. Incertain video coding technologies, merge mode can be an inter pictureprediction submode where the motion vector is derived from one or moremotion vector predictors without the benefit of a coded motion vectorcomponent outside the predictors. In certain other video codingtechnologies, a motion vector component applicable to the subject blockmay be present. In an example, the video encoder (603) includes othercomponents, such as a mode decision module (not shown) to determine themode of the processing blocks.

In the FIG. 6 example, the video encoder (603) includes the interencoder (630), an intra encoder (622), a residue calculator (623), aswitch (626), a residue encoder (624), a general controller (621), andan entropy encoder (625) coupled together as shown in FIG. 6.

The inter encoder (630) is configured to receive the samples of thecurrent block (e.g., a processing block), compare the block to one ormore reference blocks in reference pictures (e.g., blocks in previouspictures and later pictures), generate inter prediction information(e.g., description of redundant information according to inter encodingtechnique, motion vectors, merge mode information), and calculate interprediction results (e.g., predicted block) based on the inter predictioninformation using any suitable technique. In some examples, thereference pictures are decoded reference pictures that are decoded basedon the encoded video information.

The intra encoder (622) is configured to receive the samples of thecurrent block (e.g., a processing block), in some cases compare theblock to blocks already coded in the same picture, generate quantizedcoefficients after transform, and in some cases also intra predictioninformation (e.g., an intra prediction direction information accordingto one or more intra encoding techniques). In an example, the intraencoder (622) also calculates intra prediction results (e.g., predictedblock) based on the intra prediction information and reference blocks inthe same picture.

The general controller (621) is configured to determine general controldata and control other components of the video encoder (603) based onthe general control data. In an example, the general controller (621)determines the mode of the block, and provides a control signal to theswitch (626) based on the mode. For example, when the mode is the intramode, the general controller (621) controls the switch (626) to selectthe intra mode result for use by the residue calculator (623), andcontrols the entropy encoder (625) to select the intra predictioninformation and include the intra prediction information in thebitstream; and when the mode is the inter mode, the general controller(621) controls the switch (626) to select the inter prediction resultfor use by the residue calculator (623), and controls the entropyencoder (625) to select the inter prediction information and include theinter prediction information in the bitstream.

The residue calculator (623) is configured to calculate a difference(residue data) between the received block and prediction resultsselected from the intra encoder (622) or the inter encoder (630). Theresidue encoder (624) is configured to operate based on the residue datato encode the residue data to generate the transform coefficients. In anexample, the residue encoder (624) is configured to convert the residuedata from a spatial domain to a frequency domain, and generate thetransform coefficients. The transform coefficients are then subject toquantization processing to obtain quantized transform coefficients. Invarious embodiments, the video encoder (603) also includes a residuedecoder (628). The residue decoder (628) is configured to performinverse-transform, and generate the decoded residue data. The decodedresidue data can be suitably used by the intra encoder (622) and theinter encoder (630). For example, the inter encoder (630) can generatedecoded blocks based on the decoded residue data and inter predictioninformation, and the intra encoder (622) can generate decoded blocksbased on the decoded residue data and the intra prediction information.The decoded blocks are suitably processed to generate decoded picturesand the decoded pictures can be buffered in a memory circuit (not shown)and used as reference pictures in some examples.

The entropy encoder (625) is configured to format the bitstream toinclude the encoded block. The entropy encoder (625) is configured toinclude various information according to a suitable standard, such asthe HEVC standard. In an example, the entropy encoder (625) isconfigured to include the general control data, the selected predictioninformation (e.g., intra prediction information or inter predictioninformation), the residue information, and other suitable information inthe bitstream. Note that, according to the disclosed subject matter,when coding a block in the merge submode of either inter mode orbi-prediction mode, there is no residue information.

FIG. 7 shows a diagram of a video decoder (710) according to anotherembodiment of the disclosure. The video decoder (710) is configured toreceive coded pictures that are part of a coded video sequence, anddecode the coded pictures to generate reconstructed pictures. In anexample, the video decoder (710) is used in the place of the videodecoder (310) in the FIG. 3 example.

In the FIG. 7 example, the video decoder (710) includes an entropydecoder (771), an inter decoder (780), a residue decoder (773), areconstruction module (774), and an intra decoder (772) coupled togetheras shown in FIG. 7.

The entropy decoder (771) can be configured to reconstruct, from thecoded picture, certain symbols that represent the syntax elements ofwhich the coded picture is made up. Such symbols can include, forexample, the mode in which a block is coded (such as, for example, intramode, inter mode, bi-predicted mode, the latter two in merge submode oranother submode), prediction information (such as, for example, intraprediction information or inter prediction information) that canidentify certain sample or metadata that is used for prediction by theintra decoder (772) or the inter decoder (780), respectively, residualinformation in the form of, for example, quantized transformcoefficients, and the like. In an example, when the prediction mode isinter or bi-predicted mode, the inter prediction information is providedto the inter decoder (780); and when the prediction type is the intraprediction type, the intra prediction information is provided to theintra decoder (772). The residual information can be subject to inversequantization and is provided to the residue decoder (773).

The inter decoder (780) is configured to receive the inter predictioninformation, and generate inter prediction results based on the interprediction information.

The intra decoder (772) is configured to receive the intra predictioninformation, and generate prediction results based on the intraprediction information.

The residue decoder (773) is configured to perform inverse quantizationto extract de-quantized transform coefficients, and process thede-quantized transform coefficients to convert the residual from thefrequency domain to the spatial domain. The residue decoder (773) mayalso require certain control information (to include the QuantizerParameter (QP)), and that information may be provided by the entropydecoder (771) (data path not depicted as this may be low volume controlinformation only).

The reconstruction module (774) is configured to combine, in the spatialdomain, the residual as output by the residue decoder (773) and theprediction results (as output by the inter or intra prediction modulesas the case may be) to form a reconstructed block, that may be part ofthe reconstructed picture, which in turn may be part of thereconstructed video. It is noted that other suitable operations, such asa deblocking operation and the like, can be performed to improve thevisual quality.

It is noted that the video encoders (303), (503), and (603), and thevideo decoders (310), (410), and (710) can be implemented using anysuitable technique. In an embodiment, the video encoders (303), (503),and (603), and the video decoders (310), (410), and (710) can beimplemented using one or more integrated circuits. In anotherembodiment, the video encoders (303), (503), and (503), and the videodecoders (310), (410), and (710) can be implemented using one or moreprocessors that execute software instructions.

Block based compensation from a different picture may be referred to asmotion compensation. Block compensation may also be done from apreviously reconstructed area within the same picture, which may bereferred to as intra picture block compensation, intra block copy (IBC),or current picture referencing (CPR). For example, a displacement vectorthat indicates an offset between a current block and the reference blockis referred to as a block vector. According to some embodiments, a blockvector points to a reference block that is already reconstructed andavailable for reference. Also, for parallel processing consideration, areference area that is beyond a tile/slice boundary or wavefrontladder-shaped boundary may also be excluded from being referenced by theblock vector. Due to these constraints, a block vector may be differentfrom a motion vector in motion compensation, where the motion vector canbe at any value (positive or negative, at either x or y direction).

The coding of a block vector may be either explicit or implicit. In anexplicit mode, which is sometimes referred to as (Advanced Motion VectorPrediction) AMVP mode in inter coding, the difference between a blockvector and its predictor is signaled. In the implicit mode, the blockvector is recovered from the block vector's predictor, in a similar wayas a motion vector in merge mode. The resolution of a block vector, insome embodiments, is restricted to integer positions. In otherembodiments, the resolution of a block vector may be allowed to point tofractional positions.

The use of IBC at the block level may be signaled using a block levelflag, referred to as an IBC flag. In one embodiment, the IBC flag issignaled when a current block is not coded in merge mode. The IBC flagmay also be signaled by a reference index approach, which is performedby treating the current decoded picture as a reference picture. In HEVCScreen Content Coding (SCC), such a reference picture is put in the lastposition of the list. This special reference picture may also be managedtogether with other temporal reference pictures in the DPB. IBC may alsoinclude variations such as flipped IBC (e.g., the reference block isflipped horizontally or vertically before used to predict currentblock), or line based (IBC) (e.g., each compensation unit inside an M×Ncoding block is an M×1 or 1×N line).

FIG. 8 illustrates an embodiment of intra picture block compensation(e.g., IBC mode). In FIG. 8, a current picture 800 includes a set ofblock regions that have already been coded/decoded (i.e., gray coloredsquares) and a set of block regions that have yet to be coded/decoded(i.e., white colored squares). A block 802 of one of the block regionsthat have yet to be coded/decoded may be associated with a block vector804 that points to another block 806 that has previously beencoded/decoded. Accordingly, any motion information associated with theblock 806 may be used for the coding/decoding of block 802.

According to some embodiments, the reconstructed samples of the currentpicture are stored in a dedicated memory. Due to the cost of storingreconstructed samples in a dedicated memory, the reference area isgenerally not as large as a full frame, but instead, is up to the memorysize. In some examples, the IBC refers to only some neighboring areas,but not the whole picture. In one example, the memory size is one CTU,which means that only when the reference block is within the same CTU asthe current block, the IBC mode can be used. In another example, thememory size is two CTUs, which means that only when the reference blockis either within the current CTU, or the CTU to the left of current CTU,the IBC mode can be used. In these examples, when the reference block isoutside the designated local area, even if the reference block has beenreconstructed, the reference samples cannot be used for intra pictureblock compensation.

With the constrained reference area, the efficiency of IBC is limited.Accordingly, there is a need to further improve the efficiency of IBCwith a constrained reference area. Embodiments of the present disclosureprovide improved efficiency of IBC with a constrained reference area.

According to some embodiments, when the multi-hypothesis prediction isapplied to improve an intra prediction mode, multi-hypothesis predictioncombines one intra prediction and one merge indexed prediction. For a CUcoded in the merge mode, one flag may be signaled for the merge mode toselect an intra mode from an intra candidate list when the flag is true.

In some embodiments, for the luma component, the intra candidate list isderived from 4 intra prediction modes including DC, planar, horizontal,and vertical modes, and the size of the intra candidate list may be 3 or4 depending on the block shape. The intra candidate list is not limitedthe previously listed 4 intra prediction modes, and can include anydesired number of intra prediction directions. For example, when the CUwidth is two times larger than the CU height, the horizontal mode isexcluded from the intra candidate list, and when the CU height is twotimes larger than the CU width, the vertical mode is excluded from theintra candidate list. In some embodiments, one intra prediction modecandidate selected in accordance with an intra mode index and one mergemode prediction candidate selected in accordance with a merge index arecombined using a weighted average. In some embodiments, for the chromacomponent, the direct mode (DM) is applied without extra signaling.

According to some embodiments, the weights for combining predictions maybe implemented as follows. When the DC or planar mode is selected, orthe CB width or height is smaller than 4, equal weights are applied tothe intra and inter prediction candidates. In some examples, for thoseCBs with a CB width and height larger than or equal to 4, when thehorizontal/vertical mode is selected, one CB may be first vertically orhorizontally split into four equal-area regions. Each weight set,denoted as (w_intra_(i), w_inter_(i)), where i is from 1 to 4, may beimplemented as follows: (w_intra₁, w_inter₁)=(6, 2), (w_intra₂,w_inter₂)=(5, 3), (w_intra₃, w_inter₃)=(3, 5), and (w_intra₄,w_inter₄)=(2, 6). These weight sets may be applied to a correspondingregion, where (w_intra₁, w_inter₁) is for the region closest to thereference samples, and (w_intra₄, w_inter₄) is for the region farthestaway from the reference samples. After the weight sets are applied to acorresponding region, the combined prediction may be calculated bysumming up the two weighted predictions and right-shifting 3 bits.Furthermore, the intra prediction mode for the intra prediction part maybe saved for reference by the following neighboring CUs.

FIG. 9 illustrates an example of multi-hypothesis prediction. InterPredictor (i) (922) and Intra Predictor (i) (924) correspond to theinter prediction and intra prediction parts for the i^(th) region. Theweights w_inter(i) and w_intra(i) correspond to the inter prediction andintra prediction weights, respectively, for the i^(th) region. The FinalPredictor (912) may be formed by combining the weighted Inter Predictor(922) and Intra Predictor (924). A current block (910) may bereconstructed using the final predictor (912) and residual samples(914). The residual sample may represent a difference between thecurrent block (910) and the Final Predictor (912).

Generally, motion vectors are used for finding a reference block fromanother reference picture other than the current picture. However, whenintra-inter blending mode is used, current prediction modes do notspecify how to use both a motion vector and a block vector. Accordingly,there is a need to develop methods to support the method of usingintra-inter blending mode when both motion compensation and IBC isallowed.

According to embodiments of the present disclosure, the term block maybe interpreted as a prediction block, a coding block, or a coding unit(i.e., CU).

According to some embodiments, when the IBC mode is used, block vectorsare excluded from a candidate list such as a merge mode candidate listwhen forming the inter predictor part in the intra-inter blending mode.For example, when a merge candidate is coded in the IBC mode, the mergecandidate is considered as unavailable so that the block vector for thismerge candidate is not used in the intra-inter blending mode.

According to some embodiments, when a merge candidate is coded in theIBC mode, a block vector of the merge candidate is used as the interprediction part in intra-inter blending mode. If a block vector isselected using a merge index from the candidate list, the restrictionsimposed on this block vector may be applied to other block vectors. Forexample, these restrictions may require that other block vectors (e.g.,any block vector such as the block vectors in the merge list, in thecurrent block, etc.) should be pointing to a valid reference area,assuming the whole coding unit is coded using this block vector, notjust the partition that uses this block vector.

According to some embodiments, block vectors are stored for each codingunit coded in intra-inter blending mode if the inter predictor isgenerated using a block vector. These stored block vectors may be usedfor other blocks that have yet to be reconstructed.

In some embodiments, when luma and chroma components have separatecoding tree structures (i.e., dual-tree structure), the intra-interblending mode is not used. For example, when this condition is met, theintra-inter blending mode is disabled.

In some embodiments, when the luma and chroma components have separatecoding tree structures, the use of intra-inter blending mode is allowed.For the luma component, a merge index may be signaled to select a motionvector or block vector from the candidate list, and an intra predictionmode may be signaled to select an intra prediction predictor from anintra prediction candidate list.

In some embodiments, when intra-inter blending mode is allowed for thedual-tree structure for luma and chroma components, block vectors arestored for each coding unit coded in intra-inter blending mode if theinter predictor is generated using a block vector. For the chromacomponent, in one embodiment, the chroma CU is not allowed to be codedin intra-inter blending mode. In another embodiment, the chroma CU canbe coded in intra-inter blending mode such that each smallest chromablock's block vector or motion vector is derived from the chroma block'scollocated luma sample's block vector or motion vector, provided thatthe corresponding luma sample is coded in IBC mode or an inter mode,respectively. Otherwise, if any of these smallest chroma blocks cannotderive a valid block vector or motion vector from the chroma block'scollocated luma sample, intra-inter blending mode is not allowed for theentire chroma CU.

According to some embodiments, a triangular prediction unit modeprovides a triangle partition of a CU for motion compensated prediction.As illustrated in FIG. 10, current blocks (1010A) and (1010B) are splitinto two triangular prediction units. For example, current block (1010A)is split in the diagonal direction (e.g., split from top left corner tobottom right corner) to create triangular prediction units (1012) and(1014). In another example, current block 1010B is split in the inversediagonal direction (e.g., split from top right corner to bottom leftcorner) to create triangular prediction units (1016) and (1018). Eachtriangular prediction unit in the CU may be inter-predicted using theprediction unit's own uni-prediction motion vector and reference frameindex, which may be derived from a uni-prediction candidate list. Anadaptive weighting process may be performed to the diagonal edge afterpredicting the triangular prediction units. Then, the transform andquantization process may be applied to the whole CU. In someembodiments, the triangular prediction mode is applied to the skip andmerge modes.

According to some embodiments, a uni-prediction candidate list includesfive uni-prediction motion vector candidates. The uni-predictioncandidate list may be derived from seven neighboring blocks includingfive spatial neighboring blocks and two temporal co-located blocks. Forexample, FIG. 11 illustrates a current block 1101 with neighboringblocks A0 (1102), A1 (1103), B0 (1104), B1 (1105), B2 (1106), B3 (1108),and A2 (1107). FIG. 11 further illustrates two temporal co-locatedblocks C0 (1112) and C1 (1114). The motion vectors of the sevenneighboring blocks may be collected and put into the uni-predictioncandidate list according to an order of uni-prediction motion vectors,L0 motion vector of bi-prediction motion vectors, L1 motion vector ofbi-prediction motion vectors, and averaged motion vector of the L0 andL1 motion vectors of bi-prediction motion vectors. If the number ofcandidates is less than five, a zero motion vector may be added to thelist.

According to some embodiments, after predicting each triangularprediction unit, an adaptive weighting process is applied to thediagonal edge between the two triangular prediction units to derive thefinal prediction for the whole CU. A first example of a weighting group(1^(st) weighting factor group) may include the following set ofweights: {⅞, 6/8, 4/8, 2/8, ⅛} for the luminance samples and {⅞, 4/8, ⅛}for the chrominance samples. A second example of a weighting group(2^(nd) weighting factor group) may include the following set ofweights: {⅞, 6/8, ⅝, 4/8, ⅜, 2/8, ⅛} for the luminance samples and {6/8, 4/8, 2/8} for the chrominance samples. In some embodiments, oneweighting factor group is selected based on a comparison of the motionvectors of two triangular prediction units. For example, the 2^(nd)weighting factor group may be used when the reference pictures of thetwo triangular prediction units are different from each other, or theirmotion vector difference is larger than 16 pixels. Otherwise, the 1^(st)weighting factor group is used.

FIG. 12 illustrates weighting factors applied along a diagonal edge ofblock (1200) of luminance samples, and weighting factors applied along adiagonal edge of block (1202) for chrominance samples. The areas P₁ andP₂ indicate, for example, non-weighted areas. For example, asillustrated in FIG. 12, block (1200) includes a plurality of sub-blocks,with each sub-block partitioned in accordance with the triangleprediction mode. A sub-block labeled with 7 indicates, for example, thefirst triangular prediction unit of this sub-block has a weightingfactor of ⅞, and the second triangular prediction unit of this sub-blockhas a weighting factor of ⅛.

According to some embodiments, the motion vectors (e.g., Mv1 and Mv2 forP₁ and P₂, respectively, in FIG. 12) of the triangular prediction unitsare stored in 4×4 grids. For each 4×4 grid, either a uni-prediction or abi-prediction motion vector is stored depending on the position of the4×4 grid in the block. For example, as illustrated in FIG. 13, forblocks 1300 and 1302, the uni-prediction motion vector, either Mv1 orMv2, is stored for the 4×4 grid located in the non-weighted area. Forthe weighted area, a bi-prediction motion vector is stored for the 4×4grid. The bi-prediction motion vector may be derived from Mv1 and Mv2according to the following rules:

-   -   (i) If Mv1 and Mv2 have motion vectors from different directions        (L0 or L1), Mv1 and Mv2 are combined to form the bi-prediction        motion vector. These vectors may be equally weighted in some        examples, and weighted differently in other examples.    -   (ii) If both Mv1 and Mv2 are from the same L0 (or L1) direction:        -   a. If the reference picture of Mv2 is the same as a picture            in the L1 (or L0) reference picture list, Mv2 is scaled to            the picture. Mv1 and the scaled Mv2 are combined to form the            bi-prediction motion vector.        -   b. If the reference picture of Mv1 is the same as a picture            in the L1 (or L0) reference picture list, Mv1 is scaled to            the picture. The scaled Mv1 and Mv2 are combined to form the            bi-prediction motion vector.        -   c. Otherwise, only Mv1 is stored for the weighted area.

According to some embodiments, the triangular prediction unit mode isapplied to CUs in the skip or merge mode. Generally, the block size ofthe CUs is not smaller than 8×8. However, embodiments of the presentdisclosure are not limited to this minimum size. For a CU coded in askip or merge mode, a CU level flag may be signalled to indicate whetherthe triangular prediction unit mode is applied for the current CU. Whenthe triangular prediction unit mode is applied to the CU, an indexindicating the direction for splitting the CU into two triangularprediction units and the motion vectors of the two triangular predictionunits may be signalled. The index may range from 0 to 39. A look-uptable may be used for deriving the splitting direction and motionvectors from the index. For example, the look-up table may associateeach index with a splitting direction, a motion vector, and a referencepicture.

Generally, a motion vector is used for finding a reference block fromanother reference picture other than the current picture. When triangleprediction unit mode is used, prediction modes that use motion vectorsdo not specify how to use both a block vector and a motion vector.Accordingly, there is a need to develop methods to support the method ofusing the triangle prediction unit mode when both intra block copy andinter motion compensation are present.

According to some embodiments, when forming a uni-prediction candidatelist for the triangle prediction unit mode, block vectors are excludedfrom the uni-prediction list. For example, when a neighboring block iscoded in the IBC mode, the block vector of the neighboring block isconsidered as unavailable so that the block vector does not appear inthe uni-prediction candidate list for the triangle prediction unit mode.

According to some embodiments, a candidate list generated for thetriangle prediction unit mode includes both block vectors and motionvectors. In some embodiments, if a block vector is listed in thecandidate list, the restrictions on this block vector may be imposed onother block vectors (e.g., any block vector in the current picture or inthe candidate list). For example, some of these restrictions specifythat a block vector should be pointing to a valid reference areaassuming the whole coding unit is coded using this block vector, notjust the partition that uses this block vector.

In some embodiments, if one candidate is a motion vector (e.g., referredto as a temporal reference picture) and one candidate is a block vector(e.g., referred to as the current picture), then, the two referencepictures for the two prediction units are considered different, and the2nd weighting factor group is used. In some embodiments, if bothcandidates are block vectors, then the two reference pictures for thetwo prediction units are considered the same, and the 1st weightingfactor group is used. In some embodiments, if both existing candidatesare motion vectors, two prediction units may generated using one or moreconventional methods known to one of ordinary skill in the art.

According to some embodiments, when luma and chroma units have separatecoding tree structures (e.g., dual-tree structure), the triangleprediction unit mode is not used. For example, the triangle predictionmode may be disabled when the luma and chroma units have separate codingtree structures.

According to some embodiments, when the candidate list is not filledwith five candidates, default block vectors may be used to fill up thecandidate list. These default block vectors may be in addition to thezero motion vector. In some examples, block vectors such as (−w, 0),(−2w, 0), (0, −h), (0, −2h), (−w, −h), etc, may be used as the defaultblock vectors, where w and h are the width and height, respectively ofthe current coding block. The default block vectors may be put in frontof the zero motion vector(s) or behind the zero motion vector(s) in thecandidate list.

Motion vector storage in the weighted area of the triangle predictionmode may be performed in accordance with the following embodiments,which may be combined or used separately.

In some embodiments, if a block vector is used for one triangularpartition and a motion vector is used in the other triangular partition,the block vector is not stored in the weighted area, and the motionvector is stored in the weighted area.

In some embodiments, if a block vector is used for one triangularpartition and a motion vector is used in the other triangular partition,the block vector and motion vector are stored using bi-prediction. Forexample, the block vector may be stored in the L0 bi-predictor, and themotion vector may be stored in the L1 bi-predictor. In another example,the block vector may be stored in the L1 bi-predictor, and the motionvector may be stored in the L0 bi-predictor. In another example, thevector from the first triangular prediction unit (e.g., 1012 or 1016 inFIG. 10) is stored in the L0 bi-predictor, and the vector from thesecond triangular prediction unit (e.g., 1014 or 1018 in FIG. 10) isstored in the L1 bi-predictor. In another example, the vector from thefirst triangular prediction unit (e.g., 1012 or 1016 in FIG. 10) isstored in the L1 bi-predictor, and the vector from the second triangularprediction unit (e.g., 1014 or 1018 in FIG. 10) is stored in the L0bi-predictor.

According to some embodiments, if storing block vectors usingbi-prediction is allowed, the block vectors are stored in the weightedarea if the block vectors are used in both triangular predictionpartitions. In some examples, two block vectors form a bi-predictionblock vector with the first block vector from the first triangularprediction unit stored in L0 and the second block vector from thetriangular prediction unit stored in L1.

According to some embodiments, if the IBC mode is allowed, only as auni-prediction mode, one block vector in the weighted area is stored ifblock vectors are used in both partitions. In one example, a blockvector from the first triangular prediction unit is stored. In anotherexample, a block vector from the second triangular prediction unit isstored. In another example, the stored block vector is an average of theblock vector from the first triangular prediction unit and the blockvector from the second triangular prediction unit.

FIG. 14 illustrates an embodiment of a process according to anembodiment of the present disclosure. In various embodiments, theprocess illustrated in FIG. 14 is executed by processing circuitry, suchas the processing circuitry in the terminal devices (210), (220), (230),and (240), the processing circuitry that performs functions of the videodecoder (310), (410), or (710), and the like. In some embodiments, theprocess illustrated in FIG. 14 is implemented by software instructions,thus, when the processing circuitry executes the software instructions,the processing circuitry performs the process illustrated in FIG. 14.

The process illustrated in FIG. 14 may start at step (S1400) where acandidate list is created for a current block in a current picture. Thiscandidate list may be a merge candidate list or a uni-candidate list.The process proceeds to step (S1402) where a coding mode for a candidateblock associated with the current block is determined. For example thecoding mode may be the IBC mode or the triangular intra prediction mode.

The process proceeds to step (S1404) where it is determined to add, tothe candidate list, a vector associated with the candidate block basedon the determined coding mode. In this regard, the vector associatedwith the candidate block may be added to the candidate list inaccordance with one of the embodiments described above. The processproceeds to step (S1406), where the current block is reconstructed usingat least one candidate from the candidate list. The process illustratedin FIG. 14 may terminate after step (S1406).

The techniques described above, can be implemented as computer softwareusing computer-readable instructions and physically stored in one ormore computer-readable media. For example, FIG. 15 shows a computersystem (1500) suitable for implementing certain embodiments of thedisclosed subject matter.

The computer software can be coded using any suitable machine code orcomputer language, that may be subject to assembly, compilation,linking, or like mechanisms to create code comprising instructions thatcan be executed directly, or through interpretation, micro-codeexecution, and the like, by one or more computer central processingunits (CPUs), Graphics Processing Units (GPUs), and the like.

The instructions can be executed on various types of computers orcomponents thereof, including, for example, personal computers, tabletcomputers, servers, smartphones, gaming devices, internet of thingsdevices, and the like.

The components shown in FIG. 15 for computer system (1500) are exemplaryin nature and are not intended to suggest any limitation as to the scopeof use or functionality of the computer software implementingembodiments of the present disclosure. Neither should the configurationof components be interpreted as having any dependency or requirementrelating to any one or combination of components illustrated in theexemplary embodiment of a computer system (1500).

Computer system (1500) may include certain human interface inputdevices. Such a human interface input device may be responsive to inputby one or more human users through, for example, tactile input (such as:keystrokes, swipes, data glove movements), audio input (such as: voice,clapping), visual input (such as: gestures), olfactory input (notdepicted). The human interface devices can also be used to capturecertain media not necessarily directly related to conscious input by ahuman, such as audio (such as: speech, music, ambient sound), images(such as: scanned images, photographic images obtain from a still imagecamera), video (such as two-dimensional video, three-dimensional videoincluding stereoscopic video).

Input human interface devices may include one or more of (only one ofeach depicted): keyboard (1501), mouse (1502), trackpad (1503), touchscreen (1510), data-glove (not shown), joystick (1505), microphone(1506), scanner (1507), camera (1508).

Computer system (1500) may also include certain human interface outputdevices. Such human interface output devices may be stimulating thesenses of one or more human users through, for example, tactile output,sound, light, and smell/taste. Such human interface output devices mayinclude tactile output devices (for example tactile feedback by thetouch-screen (1510), data-glove (not shown), or joystick (1505), butthere can also be tactile feedback devices that do not serve as inputdevices), audio output devices (such as: speakers (1509), headphones(not depicted)), visual output devices (such as screens (1510) toinclude CRT screens, LCD screens, plasma screens, OLED screens, eachwith or without touch-screen input capability, each with or withouttactile feedback capability—some of which may be capable to output twodimensional visual output or more than three dimensional output throughmeans such as stereographic output; virtual-reality glasses (notdepicted), holographic displays and smoke tanks (not depicted)), andprinters (not depicted).

Computer system (1500) can also include human accessible storage devicesand their associated media such as optical media including CD/DVD ROM/RW(1520) with CD/DVD or the like media (1521), thumb-drive (1522),removable hard drive or solid state drive (1523), legacy magnetic mediasuch as tape and floppy disc (not depicted), specialized ROM/ASIC/PLDbased devices such as security dongles (not depicted), and the like.

Those skilled in the art should also understand that term “computerreadable media” as used in connection with the presently disclosedsubject matter does not encompass transmission media, carrier waves, orother transitory signals.

Computer system (1500) can also include an interface to one or morecommunication networks. Networks can for example be wireless, wireline,optical. Networks can further be local, wide-area, metropolitan,vehicular and industrial, real-time, delay-tolerant, and so on. Examplesof networks include local area networks such as Ethernet, wireless LANs,cellular networks to include GSM, 3G, 4G, 5G, LTE and the like, TVwireline or wireless wide area digital networks to include cable TV,satellite TV, and terrestrial broadcast TV, vehicular and industrial toinclude CANBus, and so forth. Certain networks commonly require externalnetwork interface adapters that attached to certain general purpose dataports or peripheral buses (1549) (such as, for example USB ports of thecomputer system (1500)); others are commonly integrated into the core ofthe computer system (1500) by attachment to a system bus as describedbelow (for example Ethernet interface into a PC computer system orcellular network interface into a smartphone computer system). Using anyof these networks, computer system (1500) can communicate with otherentities. Such communication can be uni-directional, receive only (forexample, broadcast TV), uni-directional send-only (for example CANbus tocertain CANbus devices), or bi-directional, for example to othercomputer systems using local or wide area digital networks. Certainprotocols and protocol stacks can be used on each of those networks andnetwork interfaces as described above.

Aforementioned human interface devices, human-accessible storagedevices, and network interfaces can be attached to a core (1540) of thecomputer system (1500).

The core (1540) can include one or more Central Processing Units (CPU)(1541), Graphics Processing Units (GPU) (1542), specialized programmableprocessing units in the form of Field Programmable Gate Areas (FPGA)(1543), hardware accelerators for certain tasks (1544), and so forth.These devices, along with Read-only memory (ROM) (1545), Random-accessmemory (1546), internal mass storage such as internal non-useraccessible hard drives, SSDs, and the like (1547), may be connectedthrough a system bus (1548). In some computer systems, the system bus(1548) can be accessible in the form of one or more physical plugs toenable extensions by additional CPUs, GPU, and the like. The peripheraldevices can be attached either directly to the core's system bus (1548),or through a peripheral bus (1549). Architectures for a peripheral businclude PCI, USB, and the like.

CPUs (1541), GPUs (1542), FPGAs (1543), and accelerators (1544) canexecute certain instructions that, in combination, can make up theaforementioned computer code. That computer code can be stored in ROM(1545) or RAM (1546). Transitional data can also be stored in RAM(1546), whereas permanent data can be stored for example, in theinternal mass storage (1547). Fast storage and retrieve to any of thememory devices can be enabled through the use of cache memory, that canbe closely associated with one or more CPU (1541), GPU (1542), massstorage (1547), ROM (1545), RAM (1546), and the like.

The computer readable media can have computer code thereon forperforming various computer-implemented operations. The media andcomputer code can be those specially designed and constructed for thepurposes of the present disclosure, or they can be of the kind wellknown and available to those having skill in the computer software arts.

As an example and not by way of limitation, the computer system havingarchitecture (1500), and specifically the core (1540) can providefunctionality as a result of processor(s) (including CPUs, GPUs, FPGA,accelerators, and the like) executing software embodied in one or moretangible, computer-readable media. Such computer-readable media can bemedia associated with user-accessible mass storage as introduced above,as well as certain storage of the core (1540) that are of non-transitorynature, such as core-internal mass storage (1547) or ROM (1545). Thesoftware implementing various embodiments of the present disclosure canbe stored in such devices and executed by core (1540). Acomputer-readable medium can include one or more memory devices orchips, according to particular needs. The software can cause the core(1540) and specifically the processors therein (including CPU, GPU,FPGA, and the like) to execute particular processes or particular partsof particular processes described herein, including defining datastructures stored in RAM (1546) and modifying such data structuresaccording to the processes defined by the software. In addition or as analternative, the computer system can provide functionality as a resultof logic hardwired or otherwise embodied in a circuit (for example:accelerator (1544)), which can operate in place of or together withsoftware to execute particular processes or particular parts ofparticular processes described herein. Reference to software canencompass logic, and vice versa, where appropriate. Reference to acomputer-readable media can encompass a circuit (such as an integratedcircuit (IC)) storing software for execution, a circuit embodying logicfor execution, or both, where appropriate. The present disclosureencompasses any suitable combination of hardware and software.

APPENDIX A: ACRONYMS

JEM: joint exploration modelVVC: versatile video codingBMS: benchmark set

MV: Motion Vector HEVC: High Efficiency Video Coding SEI: SupplementaryEnhancement Information VUI: Video Usability Information GOPs: Groups ofPictures TUs: Transform Units, PUs: Prediction Units CTUs: Coding TreeUnits CTBs: Coding Tree Blocks PBs: Prediction Blocks HRD: HypotheticalReference Decoder SNR: Signal Noise Ratio CPUs: Central Processing UnitsGPUs: Graphics Processing Units CRT: Cathode Ray Tube LCD:Liquid-Crystal Display OLED: Organic Light-Emitting Diode CD: CompactDisc DVD: Digital Video Disc ROM: Read-Only Memory RAM: Random AccessMemory ASIC: Application-Specific Integrated Circuit PLD: ProgrammableLogic Device LAN: Local Area Network

GSM: Global System for Mobile communications

LTE: Long-Term Evolution CANBus: Controller Area Network Bus USB:Universal Serial Bus PCI: Peripheral Component Interconnect FPGA: FieldProgrammable Gate Areas

SSD: solid-state drive

IC: Integrated Circuit CU: Coding Unit

While this disclosure has described several exemplary embodiments, thereare alterations, permutations, and various substitute equivalents, whichfall within the scope of the disclosure. It will thus be appreciatedthat those skilled in the art will be able to devise numerous systemsand methods which, although not explicitly shown or described herein,embody the principles of the disclosure and are thus within the spiritand scope thereof.

(1) A method of video decoding includes creating a candidate list for acurrent block in a current picture included in a coded video bitstream;determining a coding mode for a candidate block associated with thecurrent block; determining whether to add, to the candidate list, avector associated the candidate block based on the determined codingmode; and reconstructing the current block using at least one candidatefrom the candidate list.

(2) The method of video decoding according to feature (1), in which thecurrent block is coded in the intra-inter blending mode, the candidatelist is a merge candidate list, and the candidate block is a mergecandidate.

(3) The method of video decoding according to feature (2), in which inresponse to a determination that the merge candidate is coded in anintra block copy mode, a block vector associated with the mergecandidate is excluded from the merge candidate list.

(4) The method of video decoding according to feature (2), in which inresponse to a determination that the merge candidate is coded in anintra block copy mode, a block vector associated with the mergecandidate is added to the candidate list as an inter prediction part inthe intra-inter blending mode.

(5) The method of video decoding according to feature (4), in which ablock vector is stored for each block in the current picture coded inthe intra-inter blending mode and having an inter prediction partgenerated by the corresponding block vector.

(6) The method of video decoding according to any one of features(1)-(5), in which the current block is coded in the triangle predictionunit mode, the candidate list is a uni-prediction candidate list, andthe candidate block is a block neighboring the current block.

(7) The method of video decoding according to feature (6), in which inresponse to a determination that the neighboring block is coded in anintra block copy mode, a block vector associated with the neighboringblock is excluded from the uni-prediction candidate list.

(8) The method of video decoding according to feature (6), in which inresponse to a determination that the neighboring block is coded in anintra block copy mode, a block vector associated with the neighboringblock is added to the uni-candidate list.

(9) The method of video decoding according to feature (8), in which theblock vector and a motion vector associated with the current block arestored as bidirectional predictors.

(10) The method of video decoding according to feature (9), in which theblock vector is stored as one of the L0 vector and the L1 vector, andthe motion vector is stored as the other of the L0 vector and the L1vector.

(11) A video decoder for video decoding including processing circuitryconfigured to create a candidate list for a current block in a currentpicture included in a coded video bitstream, determine a coding mode fora candidate block associated with the current block, determine whetherto add, to the candidate list, a vector associated the candidate blockbased on the determined coding mode, and reconstruct the current blockusing at least one candidate from the candidate list.

(12) The video decoder according to feature (11), in which the currentblock is coded in the intra-inter blending mode, the candidate list is amerge candidate list, and the candidate block is a merge candidate.

(13) The video decoder according to feature (12), in which in responseto a determination that the merge candidate is coded in an intra blockcopy mode, a block vector associated with the merge candidate isexcluded from the merge candidate list.

(14) The video decoder according to feature (12), in which in responseto a determination that the merge candidate is coded in an intra blockcopy mode, a block vector associated with the merge candidate is addedto the candidate list as an inter prediction part in the intra-interblending mode.

(15) The video decoder according to feature (14), in which a blockvector is stored for each block in the current picture coded in theintra-inter blending mode and having an inter prediction part generatedby the corresponding block vector.

(16) The video decoder according to any one of features (11)-(15), inwhich the current block is coded in the triangle prediction unit mode,the candidate list is a uni-prediction candidate list, and the candidateblock is a block neighboring the current block.

(17) The video decoder according to feature (16), in which in responseto a determination that the neighboring block is coded in an intra blockcopy mode, a block vector associated with the neighboring block isexcluded from the uni-prediction candidate list.

(18) The video decoder according to feature (16), in which in responseto a determination that the neighboring block is coded in an intra blockcopy mode, a block vector associated with the neighboring block is addedto the uni-candidate list.

(19) The video decoder according to feature (18), in which the blockvector and a motion vector associated with the current block are storedas bidirectional predictors.

(20) A non-transitory computer readable medium having instructionsstored therein, which when executed by a processor in a video decodercauses the processor to execute a method including creating a candidatelist for a current block in a current picture included in a coded videobitstream; determining a coding mode for a candidate block associatedwith the current block; determining whether to add, to the candidatelist, a vector associated the candidate block based on the determinedcoding mode; and reconstructing the current block using at least onecandidate from the candidate list.

What is claimed is:
 1. A method of video decoding comprising: creating acandidate list for a current block in a current picture included in acoded video bitstream; determining a coding mode for a candidate blockassociated with the current block; determining whether to add, to thecandidate list, a vector associated the candidate block based on thedetermined coding mode; and reconstructing the current block using atleast one candidate from the candidate list.
 2. The method of videodecoding according to claim 1, wherein the current block is coded in theintra-inter blending mode, the candidate list is a merge candidate list,and the candidate block is a merge candidate.
 3. The method of videodecoding according to claim 2, wherein in response to a determinationthat the merge candidate is coded in an intra block copy mode, a blockvector associated with the merge candidate is excluded from the mergecandidate list.
 4. The method of video decoding according to claim 2,wherein in response to a determination that the merge candidate is codedin an intra block copy mode, a block vector associated with the mergecandidate is added to the candidate list as an inter prediction part inthe intra-inter blending mode.
 5. The method of video decoding accordingto claim 4, wherein a block vector is stored for each block in thecurrent picture coded in the intra-inter blending mode and having aninter prediction part generated by the corresponding block vector. 6.The method of video decoding according to claim 1, wherein the currentblock is coded in the triangle prediction unit mode, the candidate listis a uni-prediction candidate list, and the candidate block is a blockneighboring the current block.
 7. The method of video decoding accordingto claim 6, wherein in response to a determination that the neighboringblock is coded in an intra block copy mode, a block vector associatedwith the neighboring block is excluded from the uni-prediction candidatelist.
 8. The method of video decoding according to claim 6, wherein inresponse to a determination that the neighboring block is coded in anintra block copy mode, a block vector associated with the neighboringblock is added to the uni-candidate list.
 9. The method of videodecoding according to claim 8, wherein the block vector and a motionvector associated with the current block are stored as bidirectionalpredictors.
 10. The method of video decoding according to claim 9,wherein the block vector is stored as one of the L0 vector and the L1vector, and the motion vector is stored as the other of the L0 vectorand the L1 vector.
 11. A video decoder for video decoding, comprising:processing circuitry configured to: create a candidate list for acurrent block in a current picture included in a coded video bitstream,determine a coding mode for a candidate block associated with thecurrent block, determine whether to add, to the candidate list, a vectorassociated the candidate block based on the determined coding mode, andreconstruct the current block using at least one candidate from thecandidate list.
 12. The video decoder according to claim 11, wherein thecurrent block is coded in the intra-inter blending mode, the candidatelist is a merge candidate list, and the candidate block is a mergecandidate.
 13. The video decoder according to claim 12, wherein inresponse to a determination that the merge candidate is coded in anintra block copy mode, a block vector associated with the mergecandidate is excluded from the merge candidate list.
 14. The videodecoder according to claim 12, wherein in response to a determinationthat the merge candidate is coded in an intra block copy mode, a blockvector associated with the merge candidate is added to the candidatelist as an inter prediction part in the intra-inter blending mode. 15.The video decoder according to claim 14, wherein a block vector isstored for each block in the current picture coded in the intra-interblending mode and having an inter prediction part generated by thecorresponding block vector.
 16. The video decoder according to claim 11,wherein the current block is coded in the triangle prediction unit mode,the candidate list is a uni-prediction candidate list, and the candidateblock is a block neighboring the current block.
 17. The video decoderaccording to claim 16, wherein in response to a determination that theneighboring block is coded in an intra block copy mode, a block vectorassociated with the neighboring block is excluded from theuni-prediction candidate list.
 18. The video decoder according to claim16, wherein in response to a determination that the neighboring block iscoded in an intra block copy mode, a block vector associated with theneighboring block is added to the uni-candidate list.
 19. The videodecoder according to claim 18, wherein the block vector and a motionvector associated with the current block are stored as bidirectionalpredictors.
 20. A non-transitory computer readable medium havinginstructions stored therein, which when executed by a processor in avideo decoder causes the processor to executed a method comprising:creating a candidate list for a current block in a current pictureincluded in a coded video bitstream; determining a coding mode for acandidate block associated with the current block; determining whetherto add, to the candidate list, a vector associated the candidate blockbased on the determined coding mode; and reconstructing the currentblock using at least one candidate from the candidate list.